Sunggyu is trying to find out why his sister, Jisoo was suffering from depression. Jisoo was a year older than him but they both studied in the same class as he was a brilliant student. He was admitted in the best university in the city but he couldn't help himself anymore and got desperate to know the truth of his sister. So, he decided to get admitted in her class and find out. Things get complicated when he falls for her best friend Babysoul who falls for the best looking guy in the class, Myungsoo.